Conventionally, there has been an impeller of a multiblade blower where a plurality of blades are disposed on outer peripheral portions of circular support plates so as to be parallel to an axis of rotation of the circular support plates. In such an impeller of a multiblade blower, oftentimes noise that arises due to an airflow passing through the blades configuring the impeller becomes a problem.
In order to reduce such noise, an impeller structure has been proposed where serrated shapes are formed on blade tips of the blades configuring the impeller to thereby prevent separation of the airflow on negative pressure surfaces of the blades, reduce vortexes that occur on the rear edges of the blades, and reduce noise (see JP-A No. 11-141494).